GLUTEN-FREE DIET: DEFINITION AND APPLICATIONS

Abstract

The treatment for celiac disease is a gluten-free (GF)
diet for life.1 This means strict avoidance of foods and
beverages that contain wheat, rye, barley and triticale (a
cross between wheat and rye). A GF diet is also required
for management of other disorders of gluten intolerance
including dermatitis herpetiformis and non-celiac gluten
sensitivity. Gluten is a generic term applied to proteins
in wheat (gliadin), barley (hordein) and rye (secalin).
Patients with poorly treated celiac disease are at risk of
several complications including nutritional deficiencies
(e.g., osteoporosis), development of other autoimmune
disorders and malignancies such as intestinal
lymphoma.
A GF diet is complex, both for understanding
and its application in everyday living. Wheat is not only
ubiquitous in our diet, wheat flour (atta) is the most
abundant and affordable staple food. Flours derived
from naturally gluten-free grains like rice, corn,
sorghum and millet provide good alternates but these
grains are more expensive and cross contamination with
wheat during milling process is almost universal. A GF
diet is significantly more expensive as patients often
have to rely on packaged food and is also socially
restrictive especially for eating out and travelling.
Because of these complexities, it is essential that
patients requiring a GF diet consult a registered dietician
skilled in this area.2 Such dietetic services are not
always readily available. In countries like Pakistan
where awareness of GF diet and regulation for food
labelling is limited, patients face far greater challenges.
Ideally, a GF diet should have zero gluten.
However, the reality is that there is some background
contamination with gluten-containing grains in many
food products. There is limited research investigating
the threshold of gluten acceptability in a GF diet. An
elegant study by Catassi et al demonstrated that as little
as 50 mg of gluten if ingested daily for a few months
can lead to villous injury.3 This is a very tiny quantity
and amounts to about 1/70th of a slice of toast. The
safety threshold of gluten ingestion will also depend on
the total amount of food consumed per day. Such
research studies are difficult to perform as they require
repeated invasive procedures (small intestinal biopsies)
to look for early villous changes.
In the past, there had been controversy about
the definition of GF diet. In Europe, gluten content of up
to 200 ppm was acceptable in a GF diet whereas in
North America the limit was set at 20 ppm. (Parts per
million is equivalent to milligrams per kilogram, i.e., 20
ppm implies 20 mg of gluten per Kg of food).
Furthermore, wheat starch was permissible in a GF diet
in Europe but not in North America. A consensus on an
international definition of GF diet has been reached only
recently. Codex Alimentarius Commission is an
international body of the Food and Agriculture
Organization of the United Nations (FAO UN) and the
World Health Organization (WHO) responsible for
setting standards for regulating foods allergens. In July
2008, the Codex Committee on Nutrition and Foods for
Special Dietary Uses revised its standard for foods to be
considered '˜gluten-free' for international trade. The
highlights of this Standard include the following:
1. Gluten-free foods do not contain wheat, rye,
barley, oats or their crossbred varieties and the
gluten level does not exceed 20 ppm (20 mg/Kg) in
total, based on the food as sold to the consumer.
and/or
2. Gluten-free foods may contain one or more
ingredients from wheat, rye, barley, oats or their
crossbred varieties which have been specially
processed to remove gluten and the gluten level does
not exceed 20 ppm (20 mg/Kg) in total, based on the
food as sold to the consumer.
3. The allowance of pure, uncontaminated oats may be
determined at the national level.
4. Foods specially processed to reduce gluten content to
a level between 20-100 ppm (20-100 mg/Kg) based
on the food as sold or distributed to the consumer
must not be labelled gluten-free. Labelling terms for
such products (e.g., low gluten, reduced gluten) and
decisions for marketing may be determined at the
national level, but must indicate the true nature of the
food.
Pure and uncontaminated oats in limited
quantities are safe for consumption by most patients
with celiac disease.5 However, because of frequent
contamination of the commercially available oats with
gluten-containing grains, they are included in the above
definition of GF diet. This standardised definition of
gluten-free is now being applied internationally and will
create uniformity for trade.
Understanding the definition of GF diet is
important not only for patients and health care
professionals but also for food manufacturers and
government agencies regulating food safety. It is the
food manufacturer's responsibility to ensure that the
gluten content of the product labelled gluten-free does
not exceed the allowed limit of 20 ppm. Gluten in wheat
J Ayub Med Coll Abbottabad 2011;23(1)
2 http://www.ayubmed.edu.pk/JAMC/23-1/Mohsin.pdf
is a mixture of gliadin and glutenin proteins, each
composed of several sub-fractions. Gluten analysis is,
therefore, a complex procedure and not routinely
available. The currently recommended test for gluten
quantification is the R5 ELISA and few laboratories are
equipped to perform the analysis accurately.
A food manufacturer in Pakistan has recently
been selling whole wheat flour (atta) by marketing it as
'˜gluten-free'. Gluten in wheat is what gives its flour the
binding capacity and currently there is no technology
available to remove all gluten from wheat and still
maintain its characteristic as flour. The manufacturer's
claim in this case is clearly misleading and will
jeopardise the health of patients on GF diet. Due to a
lack of good understanding of a GF diet, it is easy for
patients (and physicians) to succumb to such claims. In
addition, because of poor health safety regulations, the
government authorities have not taken any measures to
address this serious problem.
In summary, patients, health care
professionals, food industry and government regulatory
agencies all need to learn about GF diet. Patients must
be vigilant about label reading. Any claims of a product
being gluten-free should be critically evaluated with
appropriate testing. The government should enact strict
food labelling legislation and scrutinise any
manufacturer claiming to make GF products to ensure
the health of patients on a GF diet.